Automatic regulator for compressors



Nov. 3, 1953 J. A. BOREL 2,657,850

AUTOMATIC REGULATOR FOR COMPRESSORS Filed Nov. 21, 1949 Fig. I

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JOsep/L' Abel Borel 6 am fm ATTORNEYS Patented Nov. 3, 1 953 AUTOMATIC REGUEATOR FOR OOMPRESSORS Joseph Abel: Borel, Paris, France, assignor to Societe Schneider and. nership of France Ole, Paris, France, a part- Application November 21,1949, Serial No;v 1283641 Claims. priority, application France November 25, 1948 10 Claims. 1,

In a compressor driven by an electric motor or an internal combustion engine or the like and required to deliver a constant pressure, being fed at a pressure, which may vary between more or less widely spaced limits, it is important from an economic point of view to regulate the operation of the compressor in such a way that the power required from the motor or the engine should also be approximately constant.

It is therefore an object of the present invention to provide for compressors of the positive displacement type with constant discharge. pressure, an automatic regulator which will automatically control the compressing process in such a manner that for a variable inlet pressure the required' power will be approximately constant.

It is a further object of the present invention to provide a. novel automatic regulator for compressors which is of simple construction and which i eliicient and reliable in operation.

The novel regulator of the present invention includes a relief valve which is mounted in the cylinder of the compressor if the latter is asingle stage compressor, or is mounted in the first cylindex of the compressor if the latter is a multiple stage compressor. This relief valve is mounted in the cylinder, in known manner, to regulate the compression ratio in said cylinder by remaining open during a part or all of the compression stroke to control the point at which effective compression begins. This relief valve is hydraulically operated by a pump having an adjustable output. The plunger of this pump is driven by a cam carried by the crank shaft of the compressor to furnish for each compression stroke the power required to open the relief valve. The plunger of the pump includes a ramp which controls the volume of liquid subject to the action of the pump, as will. more fully appear hereinafter, and thus controls the operation of the re--' lief valve.

This new automatic compressor regulator also includes an auxiliary servo-motor to regulate the liquid output of the pump. This servo-motor includes movable member which is displaced by variations in the intake pressure or the compressor and which i connected to the plunger of the pump so as to adjust it angu'larly and by such angular adjustments automatically control, in accordance with variations in the intake pressure, the duration of the delivery impulses of the pump and consequently the duration of the periodic openings of the relief valve.

It follows, therefore, that thi novel combination, which retards or advances the point at ventional piston 2'.

which effective compression begins as the intake pressure of the compressor increases or decreases, controls the operation of the compressor 50 that an approximately constant value is obtained for the power absorbed by the compressor.

This invention is capable of various mechanical embodiments one of which is shown more or less schematically in the accompanying drawing. This illustrative embodiment of the present invention is shown in the drawing and is described hereinafter for the purpose of illustrating the invention and should not be construed as defining or limiting the same. Reference should therefore be had to the appended claims to determine the scope of'this invention.

In the drawing:

Fig. 1 is a diagrammatic view of an embodi-- ment of the present invention;

Fig. 2 is a diagrammatic side view of the cam actuating the piston of the pump showing its angular position tothe crank pin; and

Fig. 3 is a diagrammatic showing in larger scale of the positions of the ramp, and of the piston for the several angular positions of its actuating cam.

In the drawing, the first cylinder of a multiple stage compressor or the single cylinder of a single stage compressor of positive displacement type is shown at I and is provided with a con- A relief valve 3 mounted in the upper end of cylinder l connects the latter with a suitable chamber 4 itself connected to the intake of the compressor. Valve 3 is held in closed position by spring 5.

.Piston 5, mounted in a suitable cylinder 1, which may be a part of the housing surrounding spring 5', engages relief valve 3 to open the same against the action of spring 5 and is moved in cylinder 1 by liquid under pressure provided by a pump generally indicated at 8. Pump 8 is connected to cylinder 1 through a suitable. conduit 9.

Pump 8 includes any suitable pump body in which a plunger H is working. Plunger H is provided at its upper end with an inclined ramp it. A conduit ll! is formed in plunger I l to connect the chambers above and below ramp l2. Plunger I! may be rotated through a part of a revolution by pins 14' which are carried in slots is provided in the skirt of a pinion [3 which in turn engages and is rotated by a rack l6. Rack #6 is formed integrally with or is connected to a. piston [1 working in a cylinder [8. Piston I! is subject to the pressure of a liquid provided in reservoir l9. Reservoir I9 is connected to cylinder [8 by a. suitable conduit 20. A spring 2| is 3 provided to urge piston l1 to the right, as seen in the drawing, and the tension of spring 2| is adjustable by suitably adjusting the position of nut 22. The upper part of reservoir I9 i suitably connected as by conduit 23 with the intake of the compressor.

A spring 33 is interposed between a washer 34 mounted beneath pinion I3 and a flange 35 secured to piston II to urge piston II in a downward direction.

In Fig. 2, which shows a diagrammatic side view of cam 28 and its position with respect to crank pin 32 of the crank shaft which drives the piston 2 of the compressor, the angles a, b, c, and (1 indicate the portions of the profile of the cam which control the movement of the piston H of the pump.

The angle a corresponds to the smallest stroke of the piston for which the ramp l2 uncovers the orifice 30 after having it covered; this stroke of the piston has caused a partial opening of the valve 3 before the crank pin 32 has arrived at the lower dead center A (the end of the suction stroke of the piston 2) The angle b corresponds to the position of the piston H at which the lower portion 3| of the ramp I2 is located directly below the level of the orifice 30 whatever the angular position of ramp The angle corresponds to a small additional upward movement of piston II which ends when crank pin 32 reaches its upper dead center B (end of the compression).

The angle 41 corresponds to the downward stroke of piston ll; it represents the displacement between crank pin 32 and the start 0 of the cam.

The angle e corresponds to a partial upward movement of piston H at the moment when piston II uncovers the orifice 30 for one of the intermediate angular positions which the ramp l2 can occupy.

In Fig. 3, which shows diagrammatically the developed profile of the ramp l2 and the relative vertical positions of this ramp in relation to the orifice 3!}, the vertical distances a, b, c and (1 correspond respectively to the angles of rotation a, b, c and d of the cam 28 as seen in Fig. 2. The arrow F indicates the direction of the angular displacement of the ramp l2 for an increase of the suction pressure.

Pump 8 provided with liquid from the reservoir 25 which contains liquid under slight pressure. Reservoir 25 is connected to pump 8 by conduit 24.

A suitable cam and is provided with lows a suitable cam follower 26 engages piston H a cam roller 21 which fol- 28 carried by crank shaft 2-3 of the compressor. This arrangement of cam 28 and cam follower 25 engaging piston ll raises the same in pump 8 for each turn of the crank shaft 29 cf the compressor.

With this illustrative embodiment of the present invention set up as described, when the compressor is started and crank shaft 29 is rotated by the motor driving the compressor the liquid in reservoir I6 is subject to the pressure in the intake of the compressor and this liquid acts on piston ii, and against the action of spring 2|, to vary the position of piston l1 for each value of the said intake pressure. Displacement of piston i1 is transmitted by rack l6 to pinion l3 which in turn rotates plunger II and angularly displaces ramp i2.

Ram l2 thus occupies different angular positions with respect to orifice 30 through which the conduit 24 opens into the body of the pump 8.

During each compression stroke piston II is elevated by cam 28 and executes its entire upward stroke 17 plus 0 and then it goes down under the action of the spring 33 (stroke d).

The ramp [2 first covers orifice 30 and the liquid which is above piston H is forced through the conduit 9 toward the chamber 1 where it opens valve 3.

When the suction pressure is at its lowest predetermined value piston l1 and rack l6 rotate ramp l2 so that when piston II has completed the vertical stroke a (Fig. 3) ramp l2 will uncover orifice 30 before crank pin 32 has reached its lower dead center A (end of the suction). The liquid which is located above piston II can fiow out through the conduit ID by the action of spring 5 upon piston 6 and toward the reservoir 25. The valve 3 is then closed and the effective compression takes place during the entire upward stroke of the piston 2.

When the suction pressure i at its highest predetermined value rack It has rotated ramp I2 in such a manner that orifice 30 is not uncovered by the lower portion 3| of ramp l2 until piston II has completed stroke b (Fig. 3). Valve 3 is closed and the effective compression start in cylinder 1 of the compressor; it is effective until crank pin 32 arrives at its upper dead center B, while piston l I completes its stroke 0.

When the suction pressure is at an intermediate value between the lowest and highest predetermined pressures the position of ramp I2 is such that its inclined portion uncovers orifice 30 after a stroke e of piston ll; valve 3 is closed and at this moment the effective compression begins in the cylinder l.

The predetermined values under which the device functions as indicated above can be modineed either by adjusting regulator nut 22 or by modifying the characteristics of the spring 2|.

Increase or decrease in the duration of the periodic openings of relief valve 3 retards or advances the point at which effective compression in cylinder l of the compressor begins, thus providing an almost constant pressure and an almost constant power demand by the compressor.

It will now be apparent to those skilled in the art that by the present invention there is provided a novel automatic regulator for compressors which by means of a relatively simple structure provides an efficient and reliable control of a relief valve in a cylinder of the compressor to maintain the pressure of the compressor approximately constant and thus to keep at constant level the power required from the engine driving the compressor.

Changes to or modifications of the above described illustrative embodiment of this invention may now be apparent to those skilled in the art and reference should be had to the appended claims to determine the scope thereof.

What is claimed is:

1. In a regulator for compressors including a cylinder, 9, piston in said cylinder, a crankshaft for reciprocating the piston and driving means for rotating the crankshaft, a relief valve in the cylinder, hydraulic means for opening said valve, a variable discharge pump supplying liquid under pressure to said hydraulic means, cam means driven by the crankshaft for energizing said pump and hydraulic means including a piston responsive to the pressure in the intake of the compressor for increasing and decreasing the volume of discharge of said pump as the intake pressure increases and decreases.

2. A regulator as described in claim 1 in which and said pressure responsive means.

3. A regulator described in claim 1 in which said pump includes a plunger reciprocated by named piston in the opposite direction.

5. A regulator as described in claim 4 in which variable discharge pump supplying fluid under and means responsive to the pressure in the intake of the compressor for rotating said plunger and said surface to control the volume of the fluid supplied by said pump to said hydraulic means.

7. A regulator as described in claim 6 in which said means for rotating said plunger and said the intake of the compressor.

8. A regulator as described in claim 7 in which said last named piston is resiliently biased in one direction.

9. In apparatus for actuating a pressure relief valve in a positive displacement type of compressor in accordance with the pressure existing in the intake of the compressor, a pump driven by the crankshaft of the compressor, hydraulic means connected to said pump for opening said relief valve, means for controlling the volume of liquid supplied by said pump to said hydraulic means and hydraulic means including a piston for energizing said controlling means responsive to the pressure existing in the intake of the compressor.

10. Apparatus as described in claim 9 in which said pump includes a plunger, a conduit in said to open and close said conduit, and means connecting said rotating means to said piston.

JOSEPH ABEL BOREL.

References Cited in the file of this patent UNITED STATES PATENTS 

